Using semi-intact (CNS-Adductor muscle-3 prs. of cirri) preparations of the marine crustacean, Semibalanus cariosus, and the isolated CNS of S. cariosis and Balanus nubilus, in conjunction with intracellular electrical recording from pairs of cells, augmented with selective natural (e.g. changes in light intensity) and electrical stimulation, I will continue to explore the neuronal circuitry involved in the normal fishing rhythm and in the Shadow Reflex. A). Continue to identify and characterize motor neurons found in the ventral ganglion that show activity correlated to the normal fishing rhythm and respond to a sudden decrease in illumination. B). Continue to identify and characterize interneurons that are presynaptic to the motor neurons as part of the strategy to analyze the circuit/network that organizes the patterned motor output and the circuit that generates the protective withdrawal- closure shadow reflex. C). Concentrate on working out the sequence and connections of the certain known shadow-activated interneurons located in the "dorsal small cell" assemblage in the supraesophageal ganglion. D). Attempt determine the role each of these neurons play in the processes named above by selective photo-inactivation of neurons using the dye Lucifer Yellow or 5,6 Carboxyfluorescein coupled with illunination with "intense blue light" (ca 425 nm). E). Initiate a new study of what is presumed to be sensory feed- back onto shadow-activated inerneurons that occur early in the circuit (A-Cells and I-Cells) in an attempt to explain some of the variability of the behavioral response to shadows. F). Study selected synapses in an attempt to identify the neurotransmitters used in central pathways of these circuits using simultaneous recording from pairs of cells where the connectivity becomes known. This study should contribute to an understanding of pattern- generating motor circuits, the way in which sensory information is processed through to the motor output, and the spatial organization of a network that controls a significant amount of the behavior of the animal.